This invention relates to a seat elevation adjuster for adjusting the elevation of a seat, in particular to an actuator mechanism for use in such seat elevation adjuster.
FIG. 8 shows an example of a conventional seat elevation adjuster 200 which is disclosed in Japanese Unexamined Patent Publication No. 62-275853. This seat elevation adjuster 200 comprises a first gear 203 which is supported rotatably about a first shaft 202 at a forward position of a base frame 201 (at left in FIG. 8), a second gear 205 of a smaller diameter than the first gear 203 supported rotatably about a second shaft 204, a connecting rod 207 swingably supported on a crankpin 206 projecting from one side of the first gear 203, and a bell crank 210 whose one end is supported rotatable about a third shaft 208 at a rear end of the connecting rod 207, a central angled end of the bell crank 210 being rotatably supported about a fourth shaft 209.
The second shaft 204 is fitted with an actuating knob 211 which rotates together with the second shaft 204 about its axis. When the actuating knob 211 is turned in forward and reverse directions, its rotating motion is transmitted to the connecting rod 207 through the second gear 205, the first gear 203 and the crankpin 206, and resultant forward and backward movements of the connecting rod 207 cause the bell crank 210 to swing forward and backward about the fourth shaft 209 via the third shaft 208.
A cushion frame 212 supporting an unillustrated seat bottom is connected at its forward part to the base frame 201 by a link rod and a rear end of the cushion frame 212 is joined to the other end of the bell crank 210 rotatably about a fifth shaft 213. Thus, when the actuating knob 211 is turned about the second shaft 204 in the forward and reverse directions, the bell crank 210 turns in its forward and reverse directions about the fourth shaft 209. As a result, the cushion frame 212 is caused to ascend and descend via the fifth shaft 213, whereby the elevation of the seat bottom is adjusted.
When a person is seated on the seat bottom supported by the aforementioned conventional seat elevation adjuster 200, the weight of the person is transmitted to the cushion frame 212, the bell crank 210, the connecting rod 207, the first gear 203 and the second gear 205, and resultant movements of the individual components cause the cushion frame 212 to descend. A previous approach for overcoming this problem is found in Japanese Unexamined Utility Model Publication No. 7-19562, which employs a so-called brake drum placed between the second shaft 204 and the actuating knob 211. This brake drum works in a unidirectional fashion, that is, although the brake drum allows rotational motion of the actuating knob 211 to be transmitted to the second shaft 204, rotational motion of the second shaft 204 is not transmitted in the reverse direction.
The provision of the brake drum of this kind, however, has a problem that it makes the structure of a seat elevation adjuster extremely complex, resulting in an increase in the number of components and in man-hours required for assembly, and an eventual increase in manufacturing cost.
In addition, when the seated person attempts to adjust the elevation of the seat bottom which supports his or her weight, the seated person has to turn the actuating knob 211 by hand a number of times, working against resisting forces produced by his or her own weight. Here, a problem arises that it is not easy for the seated person to adjust the elevation of the seat bottom because a large amount of force is exerted on his or her fingers when turning the actuating knob 211.
It is an object of the invention to provide a seat elevation adjuster and an actuator mechanism which are free from the problems residing in the prior art.
It is another object of the invention to provide a seat elevation adjuster and an actuator mechanism which are easy to operate and, yet, have a simpler structure.
According to an aspect of the invention, a seat elevation adjuster is provided with a seat support frame for supporting a seat, an elevation mechanism for moving the seat support frame up and down, and an actuator mechanism for actuating the elevation mechanism. The actuator mechanism comprises a rotary member rotatable in the opposite directions about a center axis to actuate the seat elevation adjuster. There are further provided a locking member which is engageable with the rotary member to keep the rotary member from rotating, and disengageable from the rotary member to allow the rotary member to rotate; and a driver member which is rotatable about the center axis, and is movable in a first direction perpendicularly intersecting the center axis and a second direction opposite to the first direction, and is engageable with the rotary member. The driver member makes the locking member to engage with the rotary member, and disengages from the rotary member when moved in the first direction, and makes the locking member to disengage from the rotary member, and engages with the rotary member when moved in the second direction to thereby permit the rotary member to rotate with a rotation of the driver member to actuate the seat elevation adjuster.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments/examples with reference to the accompanying drawings.